I will chirp in here. I have been around many, many bears: Black, Brown, and Griz (haven't encountered a Polar or Growler yet). A Couple of these events have been at 10 yards!
I have also worked as a paramedic and have treated more than a handful of folk who were chewed on.
That being said, I have not been in a situation where I had to defend myself against a bear (not to say that others haven't; indeed I know of a few). It has been my experience that if the bear knows you are there, or if you talk at the bear if they don't, they will very expiditiously depart from your presence! Now, if they don't have a good way out, that may be right over the top of you!
If, perhaps you would need to defend yourself from a charging bear, it is doubtful that anything short of a 1 oz. 12ga. Brenake Slug will slow or stop the bear. You may kill it alright, but I am reminded of the quote on the film "Mountain Men" from the character Hatchet Jack... "this here Hawkin' kilt the bar that kilt me".
Be aware of your surroundings, be willing to back away from a situation, don't freak out if you see a bear and things will likely go well with you. Good luck.
